Projection screen

ABSTRACT

A reflection-type projection screen comprising a support, the surface of which has a metallic luster, having coated thereon a light scattering layer comprising oil-containing microcapsules and a binder.

United States Patent Shizuo Miyano;

Asaji Kondo, both of Asaka-shi, Japan 855,174 1 Sept. 4, 1969 Oct. 12,1971 Fuji Photo Film Co., Ltd.

Kanagawa, Japan Sept. 4, 1968 Japan lnventors App]. No. Filed PatentedAssignee Priority PROJECTION SCREEN 13 Claims, 3 Drawing Figs.

US. Cl 350/126, 1 17/132 C Int. Cl G03b 21/60 Field of Search 350/ 126;

[56] References Cited UNITED STATES PATENTS 2,180,113 11/1939 Land350/126 2,271,614 2/1942 Baselt... 350/126 2,906,169 9/1959 Saffir350/126 X 2,932,581 4/1960 Harkness et a1. 350/126 X 3,196,741 7/1965Takahashi 350/126 3,279,313 10/1966 Kowalik et a1 350/126 3,355,31111/1967 Gosselink.... 350/126UX 3,383,153 5/1968 Vetter 350/1263,398,018 8/1968 Walters 117/132 X Primary Examiner-Louis R. PrinceAssistant Examiner-Joseph W. Roskos Attorney-Sughrue, Rothwell, Mion,Zinn & Macpeak ABSTRACT: A reflection-type projection screen comprisinga support, the surface of which has a metallic luster, having coatedthereon a light scattering layer comprising oil-containing microcapsulesand a binder.

PATENTEuum 12 |97l 3.612.650

INVENTORS SHIZUO MIYANO ASAJI KONDO BY fa e KM, am,

I Mffn{ ATTORNEYS PROJECTION scnrzrzu BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to a projection screen,and more particularly to a projection screen of the reflection typecomprising a support having a reflection surface of metallic luster,and' a light scattering layer containing microcapsule-type particlescoated on said support, whereby projected images having sufficientbrightness and reduced scintillation can be observed in a light room.

2. Description of the Prior Art A movie film or a transparent positivefilm has been generally appreciated by projecting it on ascreenand'observing the reflected images thereof.

This application is usually carried out in a dark room because theefficiency of the screen is insufiicient. Namely, as

I a prior art screen, there has been used an opaque matted base such asa paper surface, cloth surface andresin surface containing a whitepigment. Therefore, the projected light scatters in all directions anddoes not effectivelycome into sight of the observers. Consequently, thebrightness of the projected image is low. Ifsuch a screen'is usedinalight room, the contrast of the image becomes very poor because theambient light is uniformly applied to the screen, which does not satisfythe demand of the observers. Thus, it is sometimes necessary, thoughundesirable, to darken a-circumference in order to increase the contrastof the image. It would be very advantageous if the projection could becarried'out in a light room.

The principal object of the present invention is to provide a reflectionscreen by which bright images maybe observed in light room, by providinga surface which reflects a greater por-- tion of the projected light andscatters the reflected light.

SUMMARY OF THE INVENTION The above object is attained by providing alight scattering. layer having a thickness of from microns to 100microns on a light reflective support having a metallic luster surface.Such a light scattering layer comprises a transparent continuous phaseand finely divided particles dispersed therein in the form ofmicrocapsules which have a different refractive index from that of thecontinuous phase. The form of the microcapsules is such that atransparent or semitransparent granular core material is surrounded andprotected by a filmforming' polymer material as the film. Theutilization of such microcap sules as the light scattering element isthe essence of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional viewshowing an embodiment of the projection screen of the invention;

FIGS. and 2b are cross-sectional viewsshowing different embodiments ofthe microcapsules as the light scattering element of the invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a light scatteringlayer 3 is laid on a support I having a metallic luster surface 2 whichreflects the light. This light scattering layer is composed ofmicrocapsules 4 and a binder 5. The surface thereof 6=is not smooth butis uneven due to the microcapsules.

FIG. 2 shows in detail the microcapsule 4 shownin FIG. I. In the Figure,(a) is a microcapsule in which a plurality of particles II is surroundedby a polymer film I2, and (b) is a microcapsule in which only oneparticle is surrounded by a polymer film 12.

As the support having the metallic luster which maybe used in thisinvention, there may be illustrated: plates, foils, plating films andvacuum-deposited films of aluminum, zinc, tin, nickel, chromium orstainless steel; a goldplate; a silver plate; a silver mirror surfaceand a silver yarn woven'cloth. Aluminum is especially advantageousbecause of its low price and large reflective ratio. A special screenwhich has directivity for the reflected lightcan be produced if analuminumplate or foil is utilized which is obtainedby compressingrolling two aluminum plates in facing relationship with one another andthen' separating the two aluminum plates. Namely, when parallel lightrays are applied to the surface having fine lines formed in onedirection by the. above rolling,the light rays are reflectedat adirect-angled phase of the lines and the scattering of the lightrays inthe phase including the lines is low.

The light scattering layerof this invention is composed of microcapsulesand a binder.

As the core materialof the microcapsules, there may be used transparentor semitransparent materials, for example, inorganic materials such asglass and silica, synthetic polymer resins such as polystyrene,polyamide, polyester and vinyl resins, solvents having a high boilingpointsuch as tricresyl phosphate, dibutyl phthalate and silicone andsolutions of polymers'dissolved in a'solvent having a high boilingpoint,

- which are used in a-grain size of from 1' micron to I00 microns.

Film forming'polymers are employed in order to produce the microcapsulesby fonningzasurrounding film around the core material. In order tomakethe microcapsules using such polymers, a well-known-method representedin, for example, Yakuzaigaku, Vol. 26, p. 1-7 (1966) by Asaji Kondo, canbe utilized.

ln:order to produce microcapsules from an aqueous solution by phaseseparation, a'method mentioned in US. Pat. No. 2,800,457 is utilized,wherein water-soluble proteins having an isoelectric point arepreferably used together with polymers having acid groups and surfaceactive agents, for example, gelatin, casein, albumin, water-solublecollagen, .gum arabic, sodium arginate, agaragar, dextran sulfate,polyvinyl methyl ether, a copolymer of polyethylene and maleic anhydrideand sodium polyvinyl benzene sulfonate. Further, when the microcapsulesare produced from an organic solvent solution by a'phase separationmethod or a polymerization method, water-soluble vinyl-polymers,cellulose, polyamide, polyester, urethane and polyurea may be used asthe film forming polymer.

Furthermore, a spray drying method can be eflectivelyutilized. Theamount of the core material should be in the range of from0.l to about10 times by weight of the film forming material. v

As the binder for the microcapsules in the light scattering layer,though known water-soluble or organic solvent soluble materials can beused, gelatin, polystyrene, polyvinyl acetal, cellulose derivatives andsaran are more useful, In such -a binder, it is preferable to have arefractive index different from that of the core material, and morepreferably, over 0.02 difference. The ratio of the microcapsules and thebinder can be determined experimentally of about l:2, by weight, so thata metallic luster surface isnot visible therethrough. In general, as'thefilm thickness of the'light scattering layer increases, the light of thescreen decreases. On the contrary, if the film is too thin the qualityof the screen deteriorates because a large amount of light is directlyreflected by the metallic lustersurface to cause glittering andhotspots. Accordingly, 5-l00 microns of film thickness is suitable.

When the screen is usedfor projectionof a color film, light scatteringlayer may be colored in neutral gray or another color at 0. l-0.5 of areflection concentration. By coloring the light scattering layer,sp'readingof the light in the light scatter- The desirablecharacteristics of this invention will be further described below:

.1. It is possible to use the screen in a light room since thebrightness is over 10 times larger than that of a prior screen.

This is because the metallic luster surface which reflects the light isused as the support.

2. The light scattering property of the screen does not decrease as muchas that of the prior art screen. This is because microcapsules are used.

3. A surface of the light scattering layer is naturally matted and thequality of the reflected images is improved due to the use ofmicrocapsules.

4. Production of the screen is easily carried out since the grain sizeof the microcapsules is easily controllable during production thereof.

5. The microcapsule itself is an excellent light scattering element ascompared with a simple particle, since the microcapsule itself is a kindof double refractive matter.

6. The screen is hard to scratch since the light scattering layer formsa tough film.

The present invention will be further illustrated by the followingexamples:

EXAMPLE 1 Production of microcapsules:

18 g. of tricresyl phosphate was dispersed in 180 g. of a 10 percentgelatin solution to prepare dispersed particles having a grain size of0.5-0.2. After mixing this emulsion with 1.8 liters of a 1 percentaqueous gum arabic solution, 35 ml. of a 2.5 percent aqueous acetic acidsolution was added to the mixture with stirring while keeping the liquidat 40 C. Thus, oilcontaining coacervation drops having a grain size of7-8p. were obtained. After cooling to 5 C., 20 ml. of formalin was addedto the system, then, a percent aqueous solution of sodium hydroxide wasadded dropwise with stirring to increase the pH of the system to 9.After letting it stand for a night, a top liquid was removed to obtain700 g. of hardened capsule slurry. Into this slurry, 800 g. of 7 percentgelatin containing a small amount of a viscous agent and a hardeningagent was added as the binder, and then water was added so as to makethe total amount 2 liters to prepare a coating.

EXAMPLE 2 Production of a reflection screen:

120 g. of the above-mentioned coating was applied to a mirror surface ofaluminum deposited on a polyester film (125 microns thickness producedby Toyo Rayon Co., Ltd.: commercial name: Metalmi) having a size of 40cm. X 50 cm.

240 g. of the coating in Example 1 was applied to a rolling aluminumplate having a 0.2 mm. thickness, 60 cm. X 80 cm. (produced by SumitomoMetal Industries, Ltd.) and dried. This aluminum plate had finelengthwise stripes thereon, which had a characteristic that scatteringof the light in a cross direction was larger than that in a lengthwisedirection.

EXAMPLE 3 Microcapsules were produced by the same procedure as inExample 1 but using a 10 percent toluene solution of polystyrene insteadof tricresyl phosphate, which were then applied to a Metalmi film toproduce a screen. The screen had' a somewhat white appearance ascompared with that in Example 1. When this screen was used in a roomlacking in light, good results were obtained.

EXAMPLE 4 solution was produced by dissolving 35 g. of ethylenediamineand 40 g. of caustic soda in 300 ml. of water. This aqueous solution wasadded dropwise to the emulsion at' room temperature with stirring. Thus,dibutylphthalate-containing polyamide capsules having a grain size of5-6;. were formed. After filtration and washing with water, theresulting capsules were dried.

Production of a screen:

As the binder, a solution was used which was produced by dissolving 50g. of polyester resin, Vitel PIE-200 (trade name, produced by GoodyearTire & Rubber Co.) in a mixture of 50 g. of methylethylketone, 20 g. ofcellosolve acetate, 30 g. of toluene and 50 g. of xylene. Into thissolution, 25 g. of the microcapsules described above was dispersed. Thedispersion was applied to the Metalmi film and dried. The amount ofapplication was 6 g. per 100 cm.

What is claimed is:

l. A reflection-type projection screen comprising a support, the surfaceof which has a metallic luster, having coated thereon a light scatteringlayer having a thickness of from 5 to 100 microns consisting essentiallyof microcapsules dispersed in a transparent continuous binder phase,said microcapsules consisting essentially of transparent orsemitransparent granular core material surrounded by a film formingpolymer material, wherein the refractive index of said microcapsules isdifferent from that of said binder phase.

2. The reflection-type projection screen as in claim 1 wherein the filmforming polymer material of said microcapsules is gelatin.

3. The reflection-type projection screen as in claim 1 wherein saidsupport is selected from the group consisting of an aluminum plate andaluminum foil which is obtained by compressively rolling two aluminumplates in facing relationship with one another and separating said twoaluminum plates.

4. The reflection-type projection screen as in claim 1 wherein said corematerial is selected from the group consisting of tricresyl phosphate,silicon and dibutyl phthalate.

5. The reflection-type projection screen as in claim 1 wherein saidbinder is selected from the group consisting of gelatin, polystyrene,polyvinyl acetal, a cellulose derivative and a vinylidene chloride-vinylchloride copolymer.

6. The reflection-type projection screen as in claim 1 wherein the coreof said microcapsules varies in size from 1 micron to 100 microns.

7. The reflection-type projection screen as in claim 1, wherein the corematerial of said microcapsules is present in a ratio of from 0.1 to 10parts, by weight, of the film forming material of said microcapsules.

8. The reflection-type projection screen as in claim I wherein theweight ratio of said microcapsules to said binder is about 1:2.

9. The reflection-type projection screen as in claim 1 wherein saidbinder differs in refractive index from the core material of saidmicrocapsules by at least 0.02.

10. A reflection-type projection screen as in claim 1 wherein saidsupport comprises aluminum.

11. The reflection-type projection screen as in claim 1 wherein saidcore material is an inorganic material selected from a group consistingof glass and silica.

12. The reflection-type projection screen as in claim 1 wherein saidcore material is a synthetic polymer resin selected from the groupconsisting of polystyrene, polyamide, polyester and vinyl resins.

13. The reflection-type projection screen as in claim 1 wherein saidcore material is a solution of a polymer dissolved in a solvent having ahigh boiling point.

2. The reflection-type projection screen as in claim 1 wherein the filmforming polymer material of said microcapsules is gelatin.
 3. Thereflection-type projection screen as in claim 1 wherein said support isselected from the group consisting of an aluminum plate and aluminumfoil which is obtained by compressively rolling two aluminum plates infacing relationship with one another and separating said two aluminumplates.
 4. The reflection-type projection screen as in claim 1 whereinsaid core material is selected from the group consisting of tricresylphosphate, silicon and dibutyl phthalate.
 5. The reflection-typeprojection screen as in claim 1 wherein said binder is selected from thegroup consisting of gelatin, polystyrene, polyvinyl acetal, a cellulosederivative and a vinylidene chloride-vinyl chloride copolymer.
 6. Thereflection-type projection screen as in claim 1 wherein the core of saidmicrocapsules varies in size from 1 micron to 100 microns.
 7. Thereflection-type projection screen as in claim 1, wherein the corematerial of said microcapsules is present in a ratio of from 0.1 to 10parts, by weight, of the film forming material of said microcapsules. 8.The reflection-type projection screen as in claim 1 wherein the weightratio of said microcapsules to said binder is about 1:
 2. 9. Thereflection-type projection screen as in claim 1 wherein said binderdiffers in refractive index from the core material of said microcapsulesby at least 0.02.
 10. A reflection-type projection screen as in claim 1wherein said support comprises aluminum.
 11. The reflection-typeprojection screen as in claim 1 wherein said core material is aninorganic material selected from a group consisting of glass and silica.12. The reflection-type projection screen as in claim 1 wherein saidcore materiAl is a synthetic polymer resin selected from the groupconsisting of polystyrene, polyamide, polyester and vinyl resins. 13.The reflection-type projection screen as in claim 1 wherein said corematerial is a solution of a polymer dissolved in a solvent having a highboiling point.